The inventive subject matter comprises is a frame supported panel utilizing four new conditions that enable weaker, lighter and thinner panels to be made stiffer and more versatile by re-configuring the panel's shape and/or by sufficiently bonding the panel to frame members. These conditions substantially increase the stiffness and load strength of these panels by many times for a dramatic increase in load carrying capacity.
There has been a long felt need to increase a panel's load capacity at little or no cost and especially that of foam or foam composite panels used as building panels for walls and roofs. Since many weaker, lighter and thinner panels have desirable properties there is a need to make them structural in order to consolidate these desirable properties into a structural product. This is especially true for polyurethane foam panels which can provide an air, vapor, moisture and thermal barrier, eliminate condensation, decrease thermal contraction and expansion and increase uplift resistance. As such, making polyurethane foam structural would provide a most comprehensive building panel.
Increasing load capacity of panels has typically been accomplished by changing the panel's design with stronger or thicker materials, by using stronger material shapes or by shortening the span between frame members, all of which have limitations and/or increase the panel's costs. In addition, it is well known that a beam or panel in a continuous condition over two or more same sized spans can carry more than a 100% increase in load capacity as compared to the same panel over a single, same sized span.
A continuous condition occurs when a beam or panel is continuous over two or more spans created by spaced apart supports or frame members. In this case the increased load capacity is caused by a reaction from a portion of a panel over one span to a sufficiently large force or load applied to the same panel over an adjacent span. As a load is applied to one span, the panel over the adjacent span(s) resists the load causing the panel to have an increased load capacity. As a result, plywood, form boards and walers all have an increased load capacity when they are continuous over two or more same sized spans. The continuous condition has only been applied to panels that are entirely above the frame members. In other words the entire continuous configured panel is above the plane created by the top edge of adjacent frame members bearing the panel. As such, it is unknown how the load capacity of a continuous panel is affected if a portion of the panel is thickened and dropped below this plane.
It is well know that the continuous condition has inside and outside spans and the insides spans have an inherently higher load capacity than the outside spans. This increased load capacity is presently wasted since most panels have only one or two inside spans and the panel's load capacity is determined by its weakest span, which is the outside span. This is an unrecognized problem and a need exists to utilize this wasted load capacity.
The continuous condition is derived from fundamental beam theory which is over 100 years old. This theory also teaches that a beam subjected to a fixed boundary condition can have a its load capacity increased up to 400%. Traditionally, a fixed boundary condition exists when the ends of a beam over a single span are fixed as opposed to being simply supported. In order to adequately fix the ends of a beam to prevent it from rotating, the entire perimeter of each end must be fixed to the frame members which only occurs if the beam is fixed to the frame member's sides, as opposed to their top. Fully fixed ends prevents beam rotation to enable the beam to use its full potential strength.
While fundamental beam theory's fixed boundary condition suggests that a material used as a beam can have its load capacity increased by 400%, the theory is silent as to its practical application, techniques and the materials to which it is applicable. Since beams are structural components, the materials typically considered for use as beams are also structural such as steel, other metals, wood and reinforced concrete. Given that such materials are rigid and have a high modulus of elasticity, it has not been known whether the fixed boundary condition can be applied to pliable, soft or otherwise weaker materials such as foams.
Despite the fact that mathematical exercises predicting an increased load capacity from a theoretical fixed boundary condition are widely known, there are few techniques by which to apply the theory and these are limited to steel, other metals and reinforced concrete. Beyond these materials there are no known techniques for attaining a 400% increase in load capacity in most other materials. As a result the practical application of the fixed boundary condition theory is unknown on most materials.
Of the two conditions, the continuous condition is widely practiced whereas the fixed boundary condition remains mostly theory. The continuous condition is the most common connection of a panel to any type of solid or framed structure. It is extensively used to attach sheathings, claddings, decks, coverings, etc. for buildings, furniture and other applications and for a variety of reasons. One important reason the continuous condition is so widely used is that it provides a continuous planar surface over frame members. On the other hand, a fixed boundary condition does not provide a continuous planar surface since its entire end perimeter theoretically needs to be fixed to the side of frame members. As such, the sole appeal of the fixed boundary condition is its theoretical increase in load capacity, which has been of little value since increasing load capacity is easily accomplished by increasing the thickness of a continuous conditioned panel. For example ⅝ inch thick plywood has about twice the load capacity as ½ inch plywood over the same span. Therefore, with such an easy and inexpensive solution to increasing a panel's load capacity there is no motivation to make the fixed boundary condition useful.
It is well known that a fixed boundary condition can be induced on steel beams by either welding or with steel bolts. This is not the case with fasteners and adhesives used to fix non-metal materials to a frame. Prior art demonstrates that some increase in load capacity has been attained using fasteners and adhesives to fix wood to a frame, although nowhere near the 400% theoretical increase possible with a fixed boundary condition. Since the success with attaining an increase in load capacity by fixing wood to a frame is severely limited as compared to fixing steel, the likelihood of attaining an increase in load capacity by fixing a much weaker material such as a foam to a frame was unexpected.
Composite action has been widely applied to wall, floor or roof assemblies, where increased load capacity or greater structural integrity of the frame members, assembly or diaphragm has been recognized by adequately bonding a sheathing to the frame members. It is also well known that polyurethane foam can be used to bond sheathing or claddings to frame members and thereby reduce racking and increase the structural integrity of an entire structural wall or roof section. However, no disclosure shows whether or not such bonding can increase the load capacity of the sheathing itself between frame members.
It is well known that structural building panels, such as plywood sheathing, require a minimum load capacity and therefore determining load capacity is fundamental to the building panel's design. For 50 years polyurethane foam has been adhesively bonded to more rigid materials and used as building panels that required the determination of the panel's load capacity in order to meet building codes and be permitted for use. In many of these cases the polyurethane foam was also adhesively bonded to frame members. However, in no case has it been recognized that bonding polyurethane foam to both the rigid material panels and to the frame members results in an increased load capacity to the polyurethane foam/rigid material composite panel. Nor has it been disclosed that polyurethane foam itself has an increased load capacity induced solely by its bond to frame members.
Moreover, polyurethane foam has been used extensively throughout the world as thermal insulation installed by bonding it to sheathing, creating a composite panel, and simultaneously bonding that composite panel to studs or trusses. Yet it has been unrecognized that this same procedure produces a continuous composite panel having a dropped section (polyurethane foam) between the studs or trusses that is bonded to frame members in a possible fixed boundary condition. Despite literally thousands of people, who have researched, designed, marketed, applied or otherwise worked with polyurethane foam in this way, no one has recognized that polyurethane foam itself or as part of a composite panel bonded to frame members can increase the panel's load capacity. Instead, the prior art is either silent about a panel's load capacity or teaches increased load capacity of the entire frame diaphragm rather than of the panels themselves. For example:
U.S. Pat. No. 3,258,889 (Richard A. Butcher) discloses a structural wall comprised of polyurethane foam bonded to the back of an interior wallboard and to the sides of studs and teaches added stiffness of the framed wall that enables the use of thinner panels and lighter frame members. U.S. Pat. No. 3,641,724 (James Palmer) discloses a wall section comprised of an exterior cover bonded to the sides of stud members by a polyurethane foam that increases the strength of the entire structure. U.S. Pat. No. 4,471,591 (Walter E. Jamison) discloses a wall assembly with an exterior section comprised of polyurethane foam bonded to sheathing and to the sides of studs. U.S. Pat. Nos. 4,748,781 & 4,914,883 (Stanley E. Wencley) discloses polyurethane fillets bonding a panel to frame members to provide an increased strength bonded structure.
U.S. Pat. No. 5,736,221 (James S. Hardigg, et al) discloses two half panels with each having a face and a web molded to the face's backside and the webs bonded together to provide a panel having bending strength in all directions. U.S. Pat. No. 8,397,465 (Jeffrey M. Hansbro et al) discloses a wall assembly comprised of polyurethane foam panels bonded to the sides of structural members (studs) and to foam boards continuous over the structural member's edge. U.S. Pat. No. 8,696,966 (Jason Smith) discloses a method of fabricating a wall structure whereby polyurethane foam is applied against a form and the foam expands to become a panel bonded to the edges and sides of support members (studs) within a wall frame. WO/2013/052997 (John Damien Digney) discloses a composite panel system reinforced with wire mesh and comprised of a structural cladding spaced apart from and bonded to a studded frame with polyurethane foam that is between and continuous over the studs.
US 2014/0053486 (Anthony Grisolia et al) discloses a wall structure including support members inside the frame (studs) and a polyurethane foam panel both continuous over and between the support members. US 2014/0115988, US 2014/0115989 and US 2014/0115991 (Michael J. Sievers, et al) discloses a wall assembly of a frame assembly with vertical members (studs) and an insulating foam layer disposed between and on top of the vertical members. US 2014/0174011 (Jason Smith) discloses a method of fabricating a wall structure comprised of bonding polyurethane foam to the edge and sides of frame members. US 2015/0093535 (James Lambach et al) discloses a framed panel with a polyiso board continuous over frame members and bonded to the sides of frame members with polyurethane foam.
None of the above or other prior art disclose that a continuous conditioned foam or foam composite panel has an increased load carry capacity solely due to a bond with frame members. Nor does the prior art disclose that there is sufficient rotational resistance in place to enable the panels to carry a larger load. Nor does the prior art disclose that a dropped section between frame members can increase the load capacity of a continuous conditioned panel. Nor are fillets, used as dropped sections, known for their ability to shorten a span so as to increase a panels' load capacity. Nor has it been disclosed that polyurethane foam can be used to create large, continuous panels over many spans to take advantage of the inside span's inherent increased load capacity.
Despite bonding foam or foam composite panels to frame members and panels with a continuous/dropped configuration used extensively for decades as building panels that required the determination of the panel's load capacity, none of the new conditions of the inventive subject matter have been previously disclosed as a bases for increasing a panel's load capacity. As such, it has not been obvious by a person of ordinary skill in the art to combine a panel's continuous condition with a fixed boundary condition to increase the panels load capacity. Nor has it been obvious to add a dropped section to a continuous conditioned panel to increase the panel's load capacity. Nor has it been obvious that rotational resistance is necessary to facilitate increases in load capacity.
The problems to be solved by this inventive subject matter are first: to increase the load carrying capacity of panels comprised of weaker, lighter and thinner materials, and second: to utilize the presently unrecognized increased load capacities of a panel's inside spans.